% 
% Usage: y = func_2(q, zeta, m, CONSTS, use_V)

function y = func_for_approx(q, zeta, m, CONSTS)
    k0    = CONSTS.k0;
    a     = CONSTS.a;
    sigma = CONSTS.sigma;
    
    if isempty(q)
        y = [];
        return;
    end
    
    y = (pi*k0*a) * besselmx(double('J'), m, k0*a*q, 0).^2 .* ...
        func_V(q, m, CONSTS) .* ...
        exp(-k0*sigma*q*zeta);
    %y = (m^2) * ...
    %    besselj(m, k0*a*q).^2 ./ func_V(q, m, CONSTS, use_V) .* ...
    %    (1/((eps*eta)^0.5)) .* exp(-k0*sigma*q*zeta);
end
